Tool wear in laser ultrasonically combined turning of tungsten carbide with PCD tools

Abstract

Tungsten carbides are typical difficult-to-cut materials due to their high hardness and brittleness, which cause severe tool wear and shorten tool life when being machined during conventional processing methods, leading to a loss of quality and accuracy of the machined parts. In this paper, a novel laser ultrasonically assisted turning technology for tungsten carbides was proposed, and the primary objective of this study was to investigate the behavior of polycrystalline diamond (PCD) tools when turning tungsten carbides with the application of ultrasonic vibration to tools and laser-induced heating to workpieces. To determine suitable parameters, thermal modeling of laser ultrasonically assisted turning of tungsten carbide was employed. Through contrast experiments carried out during conventional turning, ultrasonically elliptical vibration turning, laser-assisted turning, and laser ultrasonically combined turning of tungsten carbides with PCD tools, the tool wear characteristics and dominant wear mechanisms were investigated, and the relation between tool wear and surface quality of workpiece was determined by analyzing the effects of tool wear on the surface roughness values and the microtopography of the machined surface. A significant reduction in the cutting force and a substantial improvement in the tool life were obtained in laser ultrasonically combined turning of tungsten carbides with PCD tools when compared with conventional turning, ultrasonically elliptical vibration turning, and laser-assisted turning; therefore, lower surface roughness values and a good surface quality of the workpiece were obtained. During laser ultrasonically combined turning of tungsten carbides with PCD tools, the wear on the rake face was characterized by micro tipping and chipping, the flank face had shallow micro-grooves oriented along the cutting direction, and the dominant failure mechanisms of the PCD tools were the synergistic interaction of diffusion, oxidation, tipping, and chipping. With the increase in tool wear, the surface roughness values steadily increased in laser ultrasonically combined turning, and the cutting mode was changed from ductile mode turning to brittle mode turning, which resulted in many defects, including pits, voids, grooves, etc., on the machined surfaces.